Transcript for 'Bladerunner' Oscar Pistorius Expected to Be Charged With Premeditated Murder

where olympic sprinter oscar pistorius will be back in court tomorrow on what would have been his girlfriend's 30th birthday. Abc's rob nelson in south africa, where police are growing more confident about their case. Reporter: Tomorrow, our first look at the formal case against oscar pistorius. Nicknamed "the blade runner," pistorius will face charges in the death of his girlfriend, reeva steenkamp, who was shot multiple times through the bathroom door of his mansion. Prosecutors say it was murder. Pistorius says he mistook reeva as an intruder. What is state is now going to do, they want to show that he's a violent person. That he's a gun-toefting hot head, is the portrait they're going to paint of this man. Reporter: Prosecutors say that reeva retreated to the bathroom after a fight with pistorius. Our "20/20" team built a replica of the crime scene earlier this year, with essential questions still looming about pistorius' side of the story. How did he grab his gun from the side of the bed without noticing reeva was no longer there? We're talking about the dark of night. Reporter: Joe jackson, a defense attorney, speaking with amy robach, offered one explanation pistorius' defense could use. His attention, rightfully, is focused on what could be an intruder and the end of his life as well as her life. Reporter: Meanwhile, police told us today their case is ready. We are confident that what we have, will -- as it will come out in court -- show that, indeed, mr. Oscar pistorius has a charge to answer to. Reporter: Pistorius has completed not guilty and is free on bail. We could also learn monday exactly when this trial will begin, although it is expected to start sometime early next year. If pistorius is convicted, he faces a life sentence with a minimum of 25 years behind bars.

This transcript has been automatically generated and may not be 100% accurate.

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